CXCL9-derived peptides differentially inhibit neutrophil migration in vivo through interference with glycosaminoglycan interactions

Several acute and chronic inflammatory diseases are driven by accumulation of activated leukocytes due to enhanced chemokine expression. In addition to specific G protein-coupled receptor-dependent signaling, chemokine–glycosaminoglycan (GAG) interactions are important for chemokine activity in vivo. Therefore, the GAG–chemokine interaction has been explored as target for inhibition of chemokine activity. It was demonstrated that CXCL9(74-103) binds with high affinity to GAGs, competed with active chemokines for GAG binding and thereby inhibited CXCL8- and monosodium urate (MSU) crystal-induced neutrophil migration to joints. To evaluate the affinity and specificity of the COOH-terminal part of CXCL9 toward different GAGs in detail, we chemically synthesized several COOH-terminal CXCL9 peptides including the shorter CXCL9(74-93). Compared to CXCL9(74-103), CXCL9(74-93) showed equally high affinity for heparin and heparan sulfate (HS), but lower affinity for binding to chondroitin sulfate (CS) and cellular GAGs. Correspondingly, both peptides competed with equal efficiency for CXCL8 binding to heparin and HS but not to cellular GAGs. In addition, differences in anti-inflammatory activity between both peptides were detected in vivo. CXCL8-induced neutrophil migration to the peritoneal cavity and to the knee joint were inhibited with similar potency by intravenous or intraperitoneal injection of CXCL9(74-103) or CXCL9(74-93), but not by CXCL9(86-103). In contrast, neutrophil extravasation in the MSU crystal-induced gout model, in which multiple chemoattractants are induced, was not affected by CXCL9(74-93). This could be explained by (1) the lower affinity of CXCL9(74-93) for CS, the most abundant GAG in joints, and (2) by reduced competition with GAG binding of CXCL1, the most abundant ELR+ CXC chemokine in this gout model. Mechanistically we showed by intravital microscopy that fluorescent CXCL9(74-103) coats the vessel wall in vivo and that CXCL9(74-103) inhibits CXCL8-induced adhesion of neutrophils to the vessel wall in the murine cremaster muscle model. Thus, both affinity and specificity of chemokines and the peptides for different GAGs and the presence of specific GAGs in different tissues will determine whether competition can occur. In summary, both CXCL9 peptides inhibited neutrophil migration in vivo through interference with GAG interactions in several animal models. Shortening CXCL9(74-103) from the COOH-terminus limited its GAG-binding spectrum

Biological Activity of CXCL8 Forms Generated by Alternative Cleavage of the Signal Peptide or by Aminopeptidase-Mediated Truncation

Posttranslational modification of chemokines is one of the mechanisms that regulate leukocyte migration during inflammation. Multiple natural NH(2)-terminally truncated forms of the major human neutrophil attractant interleukin-8 or CXCL8 have been identified. Although differential activity was reported for some CXCL8 forms, no biological data are available for others.status: publishe

Truncation of CXCL8 to CXCL8(9-77) enhances actin polymerization and in vivo migration of neutrophils

CXCL8 is the principal human neutrophil-attracting chemokine and a major mediator of inflammation. The chemokine exerts its neutrophil-chemotactic and neutrophil-activating activities via interaction with glycosaminoglycans (GAGs) and activation of the G protein-coupled receptors (GPCRs) CXCR1 and CXCR2. Natural CXCL8 displays an exceptional degree of amino (NH2 )-terminal heterogeneity. Most CXCL8 forms result from proteolytic processing of authentic CXCL8(1-77). Here, we compared the potencies to activate and recruit neutrophils of the 3 most abundant natural CXCL8 forms: full-length 77 amino acid CXCL8 and the 2 major natural truncated forms lacking 5 or 8 NH2 -terminal amino acids. NH2 -terminal truncation hardly affected the capacity of CXCL8 to induce shedding of CD62L or to up-regulate the expression of the adhesion molecules CD11a, CD11b, or CD15 on human neutrophils. In addition, the potency of CXCL8 to induce neutrophil degranulation and its effect on phagocytosis remained unaltered upon removal of 5 or 8 NH2 -terminal residues. However, NH2 -terminal truncation strongly potentiated CXCL8-induced actin polymerization. CXCL8(6-77) and CXCL8(9-77) showed a comparable capacity to induce Ca2+ signaling in human neutrophils and to direct in vitro neutrophil migration. Strikingly, the ability of CXCL8(9-77) to recruit neutrophils into the peritoneal cavity of mice was significantly enhanced compared to CXCL8(6-77). These results suggest that NH2 -terminal truncation influences specific biological activities of CXCL8 and indicate that CXCL8(9-77) may be the most potent neutrophil-attracting CXCL8 form in vivo.status: publishe

Interferon-γ Orchestrates the Number and Function of Th17 Cells in Experimental Autoimmune Encephalomyelitis

Th17 cells are suggested to be pathogenic in mediating experimental autoimmune encephalomyelitis (EAE), but their relation to interferon (IFN)-γ-producing Th1 cells in vivo is not well understood. We studied the numbers and functions of Th17 cells in CREAE in Biozzi ABH mice, both in peripheral lymphoid organs and in the central nervous system. Th1 and Th17 cells alternated in secondary lymphoid organs and infiltrated into the central nervous system during chronic relapsing experimental autoimmune encephalomyelitis (CREAE). In the absence of IFN-γ the numbers and secretion of Th17 cells was enhanced, whereas exogenous administration of IFN-γ decreased the Th17 cells. In mice with intact IFN-γ genes, in vivo neutralization of interleukin (IL)-17 protected against EAE development by enhancing the number of IFN-γ-producing cells. IFN-γ knockout mice were partially protected by anti-IL-17 antibodies by decreasing cell numbers and production of IL-17. Our findings suggest that, whereas IFN-γ as such is not necessary for EAE development in the mouse, the lack of suppression of Th17 cells by IFN-γ enhances the susceptibility to develop EAE. IFN-γ thus orchestrates the number and function of Th17 cells.status: publishe

Interferon-γ orchestrates the number and function of Th17 cells in experimental autoimmune encephalomyelitis

Th17 cells are suggested to be pathogenic in mediating experimental autoimmune encephalomyelitis (EAE), but their relation to interferon (IFN)-γ-producing Th1 cells in vivo is not well understood. We studied the numbers and functions of Th17 cells in CREAE in Biozzi ABH mice, both in peripheral lymphoid organs and in the central nervous system. Th1 and Th17 cells alternated in secondary lymphoid organs and infiltrated into the central nervous system during chronic relapsing experimental autoimmune encephalomyelitis (CREAE). In the absence of IFN-γ the numbers and secretion of Th17 cells was enhanced, whereas exogenous administration of IFN-γ decreased the Th17 cells. In mice with intact IFN-γ genes, in vivo neutralization of interleukin (IL)-17 protected against EAE development by enhancing the number of IFN-γ-producing cells. IFN-γ knockout mice were partially protected by anti-IL-17 antibodies by decreasing cell numbers and production of IL-17. Our findings suggest that, whereas IFN-γ as such is not necessary for EAE development in the mouse, the lack of suppression of Th17 cells by IFN-γ enhances the susceptibility to develop EAE. IFN-γ thus orchestrates the number and function of Th17 cells. © 2011, Mary Ann Liebert, Inc

CXCR4 and CCR5 ligands cooperate in monocyte and lymphocyte migration and in inhibition of dual-tropic (R5/X4) HIV-1 infection

One of the most important functions of chemokines and their receptors is the regulation of directional migration of leukocytes within tissues. In specific tissue compartments, cells are exposed to multiple chemokines presented in complex dimensional and temporal patterns. Therefore, a leukocyte requires the mechanisms to integrate the various directional signals it receives from different chemoattractants. In this study, we report that CCL3, CCL5, and CCL8, three potent mononuclear cell chemoattractants, are able to synergize with the homeostatic chemokine CXCL12 in the migration of CD14(+) monocytes, CD3(+) T-lymphocytes, or PHA-activated lymphoblasts. In addition, CCL5 augmented the CXCR4 ligand-driven ERK phosphorylation in mononuclear cells. Furthermore, the synergistic effect between CCL5 and CXCL12 in monocyte chemotaxis is inhibited in the presence of specific CCR1 antibody and AMD3100, but not by maraviroc. In HIV-1 infection assays, a combination of CXCL12 and CCL5 cooperated to inhibit the replication of the dual-tropic (R5/X4) HIV-1 HE strain. Finally, although the dual-tropic HIV-1 strain was barely suppressed by AMD3100 or maraviroc alone, HIV-1 infection was completely blocked by the combination of these two receptor antagonists. Our data demonstrate the cooperation between CCL5 and CXCL12, which has implications in migration of monocytes/lymphocytes during inflammation and in HIV-1 infection.status: publishe

COOH-terminal SAA1 peptides fail to induce chemokines but synergize with CXCL8 and CCL3 to recruit leukocytes via FPR2.

A natural leukocyte chemoattractant was isolated from bovine serum by an established 4-step purification procedure. Based on its relative molecular mass of 7287 and NH2-terminal sequence, the protein was identified as a carboxy-terminal peptide of the acute phase protein serum amyloid A1 (SAA1). This SAA1(46-112) fragment and its human equivalent SAA1(47-104) were chemically synthesized. Unlike intact SAA1α, these SAA fragments failed to directly chemoattract neutrophils and monocytes, to induce chemokines, and to stimulate downstream extracellular signal-regulated kinase signaling in monocytes. However, the SAA fragments potently synergized with CCL3 to induce monocyte migration and with CXCL8 to stimulate neutrophil shape changes and chemotaxis. Unlike intact SAA1α, SAA1(46-112) did not induce CXCL6 ex vivo but provoked a cooperative intraperitoneal neutrophil recruitment in mice when coinjected with CXCL6 into the peritoneal cavity. Moreover, SAA1(47-104) desensitized the synergy between intact SAA1α and CXCL8 in neutrophil chemotaxis, suggesting that this peptide binds formyl peptide receptor 2 (FPR2). This was evidenced by a complete blockade of synergy between the COOH-terminal SAA1 fragments and CXCL8 or CCL3 in neutrophil and monocyte chemotaxis, respectively, by the FPR2 antagonist WRW4 Thus, SAA1 is degraded into fragments lacking chemokine-inducing capacity, while keeping synergy with cytokine-induced chemokines to sustain limited inflammation.status: publishe

Isotypic neutralizing antibodies against mouse GCP-2/CXCL6 inhibit melanoma growth and metastasis

The chemokine granulocyte chemotactic protein (GCP)-2/CXCL6 promotes tumor growth as angiogenesis inducer and neutrophil chemoattractant. The neutralizing capacity and specificity of monoclonal mouse anti-murine (mu)GCP-2/CXCL6 antibodies were evidenced by granulocyte chemotaxis and signaling assays. The half-life of the non-antigenic antibody in the blood circulation was approximately 15. days. The titers remained constant upon weekly injection. Tumor growth and lymphogenic metastases of human melanoma over-expressing muGCP-2 were reduced in mice treated with anti-muGCP-2. Moreover, the drop in muGCP-2 antibody titer correlated with the melanoma tumor size. Taken together, we show that functional blocking of GCP-2 inhibits tumor growth and metastases. © 2010 Elsevier Ireland Ltd

Isotypic neutralizing antibodies against mouse GCP-2/CXCL6 inhibit melanoma growth and metastasis

The chemokine granulocyte chemotactic protein (GCP)-2/CXCL6 promotes tumor growth as angiogenesis inducer and neutrophil chemoattractant. The neutralizing capacity and specificity of monoclonal mouse anti-murine (mu)GCP-2/CXCL6 antibodies were evidenced by granulocyte chemotaxis and signaling assays. The half-life of the non-antigenic antibody in the blood circulation was approximately 15days. The titers remained constant upon weekly injection. Tumor growth and lymphogenic metastases of human melanoma over-expressing muGCP-2 were reduced in mice treated with anti-muGCP-2. Moreover, the drop in muGCP-2 antibody titer correlated with the melanoma tumor size. Taken together, we show that functional blocking of GCP-2 inhibits tumor growth and metastases.status: publishe